Overview
The Logger class provides static methods for logging various events in the load balancer. It outputs structured, formatted log messages to the console for monitoring request flow, debugging errors, and tracking backend health status.
Static methods
request
Logs an incoming HTTP request that is being forwarded to a backend server.
static request(method: string, path: string, backendUrl: string): void
The HTTP method (GET, POST, PUT, DELETE, etc.)
The request path (e.g., “/api/users”)
The URL of the backend server receiving the request
REQUEST: GET /api/users -> http://localhost:3001
response
Logs the response received from a backend server.
static response(method: string, path: string, backendUrl: string, statusCode: number, duration: number): void
The HTTP method of the original request
The URL of the backend server that sent the response
The HTTP status code returned by the backend (200, 404, 500, etc.)
The request duration in milliseconds
RESPONSE: GET /api/users <- http://localhost:3001 [200] 45ms
error
Logs an error message, optionally associated with a specific backend server.
static error(message: string, backendUrl?: string): void
Optional URL of the backend server related to the error
ERROR: Connection refused
ERROR: Connection timeout (http://localhost:3002)
info
Logs a general informational message.
static info(message: string): void
The informational message to log
INFO: Load balancer started on port 8080
health
Logs the health status of a backend server.
static health(url: string, isHealthy: boolean, details?: string): void
The URL of the backend server being checked
Whether the backend is healthy (true) or unhealthy (false)
Optional additional details about the health check
HEALTH: HEALTHY http://localhost:3001
HEALTH: UNHEALTHY http://localhost:3002 - Connection timeout
Usage examples
Logging a complete request/response cycle
import { Logger } from './utils/logger';
const method = 'GET';
const path = '/api/users';
const backendUrl = 'http://localhost:3001';
// Log the outgoing request
Logger.request(method, path, backendUrl);
const startTime = Date.now();
// ... make the actual request ...
const duration = Date.now() - startTime;
const statusCode = 200;
// Log the received response
Logger.response(method, path, backendUrl, statusCode, duration);
REQUEST: GET /api/users -> http://localhost:3001
RESPONSE: GET /api/users <- http://localhost:3001 [200] 45ms
Logging errors
import { Logger } from './utils/logger';
// General error
Logger.error('Failed to initialize load balancer');
// Backend-specific error
const backendUrl = 'http://localhost:3002';
Logger.error('Connection refused', backendUrl);
ERROR: Failed to initialize load balancer
ERROR: Connection refused (http://localhost:3002)
Logging health checks
import { Logger } from './utils/logger';
const backends = [
'http://localhost:3001',
'http://localhost:3002',
'http://localhost:3003'
];
backends.forEach(url => {
try {
// ... perform health check ...
const isHealthy = checkHealth(url);
Logger.health(url, isHealthy);
} catch (error) {
Logger.health(url, false, error.message);
}
});
HEALTH: HEALTHY http://localhost:3001
HEALTH: UNHEALTHY http://localhost:3002 - Connection timeout
HEALTH: HEALTHY http://localhost:3003
import { Logger } from './utils/logger';
const port = 8080;
Logger.info(`Load balancer started on port ${port}`);
const backendCount = 3;
Logger.info(`Registered ${backendCount} backend servers`);
INFO: Load balancer started on port 8080
INFO: Registered 3 backend servers